Avalanche Forecast

Issued: Dec 14th, 2013 8:33AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

Avalanche Canada bcorrigan, Avalanche Canada

Additional snow, wind, and warm temperatures will determine the hazard in the next few days.

Summary

Confidence

Fair - Timing of incoming weather systems is uncertain

Weather Forecast

Sunday: Moderate snowfall with 10-15cm of accumulation, freezing levels rising up to 1800m and strong southwesterly winds. Forecast models show a bit more precipitation in the south. Freezing levels expected to remain at or near valley bottoms with tree line temperatures around -8. Ridge top winds are expected to be moderate westerlies. Monday: Little snowfall expected with less than 5cm of accumulation at higher elevations, freezing levels will rise to around 1500m with strong westerly winds. Tuesday: Moderate to locally heavy snowfall as a Pacific frontal system moves into the interior. Strong westerly winds and freezing levels rising to 1800 metres in parts of the forecast area.

Avalanche Summary

Avalanche activity has been limited to a few loose sloughs from steep terrain. On Tuesday, a wind slab avalanche size 1.5 was easily triggered under the weight of a rider on a NE aspect. Also a large ( 2.5) natural avalanche was reported in the interior of the Purcells on an E aspect. The potential exists for large destructive avalanches with increased loading.

Snowpack Summary

Recent snow and winds are adding to the surface load. Snowpack depths at tree line currently vary from 70 - 110 cm with the highest variability in wind-exposed areas. A persistent weakness of buried surface hoar and facets, along with an associated crust, is down approximately 20-40cm . This layer has been producing variable results with snowpack tests, and may become reactive as a cohesive slab develops with warming temperatures and additional loads. At the base of the snowpack are weak facets and depth hoar. This deep persistent weakness may be stubborn to trigger, especially in deeper snowpack areas, but the sensitivity to triggers likely increases in shallower locations, especially on steep, convex slopes.  At lower elevations the snow depth is below the threshold for avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs
Be cautious of terrain that has been recently wind-loaded
Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Avoid convexities or areas with a thin or variable snowpack.>Dig down to find and test weak layers before committing to a line.>Whumpfing is direct evidence of a buried instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 15th, 2013 2:00PM